To compensate for such imbalance, Lin et al. [1]} proposed a modification of the Cross Entropy Loss function, named as Focal Loss, by introducing a correction factor that hardly increases the loss function for the easy samples (i.e. down-weights inliers) but that penalises the more complex samples (i.e. up-weights outliers). See Figure REF .
\(L=-\alpha _{t}(1-p_{t})^{\gamma }log(p_{t})\) 
